This invention relates to dispensers for rolled sheet material and, in one aspect, to dispensers for paper towel rolls.
Dispensers for rolls of flexible sheet material, such as paper towel rolls, are well known. Paper towel dispensers are widely used in public lavatories to dispense paper toweling for users to dry their hands. Such dispensers typically include either a crank or lever which a user operates to drive a feed mechanism for dispensing the paper toweling. The feed mechanism typically includes a drive roller rotated by a crank or lever and an idler roller, the paper toweling is threaded between these two rollers and the idler roller is spring loaded to provide sufficient friction for rotation of the drive roller to unwind the paper toweling off a roll core. There usually is a relatively small clearance between the drive and idler rollers and the paper toweling can become backed up and cause jamming.
Some paper towel dispensing devices are capable of sequentially dispensing two rolls of paper toweling. This type dispenser is arranged so that, when all the paper toweling from a primary roll has been dispensed, the feed mechanism starts dispensing paper toweling from a reserve roll. Some multiple-roll dispensers have a transfer mechanism including a number of rollers which are arranged to provide tension between the paper toweling being unwound from the primary roll and the feed mechanism and, in response to loss of this tension, effect a transfer of paper toweling from the reserve roll into the feed mechanism. This loss of tension usually occurs when the tail end of the paper toweling has been completely unwound and detached from the primary roll core. However, a loss of tension occasionally can occur during normal use even though there still is paper on the primary roll. For example, if the primary roll core binds and the user is required to use additional force to operate the crank or lever, the primary roll can overrun after the bind is broken loose. This can cause a slack condition which is the same as a loss of tension to the transfer mechanism and it then makes a false transfer, causing paper toweling from the reserve roll to be introduced into the feed mechanism. When this occurs, the feed mechanism can become jammed and no longer capable of dispensing paper toweling or to simultaneously dispense paper toweling from both the primary and reserve rolls.
Some prior constructions which employ a series of rollers for making a transfer from the primary roll to the reserve roll are vulnerable to not effecting a transfer under some conditions which can occur during normal use. Many prior constructions are designed to dispense only one size roll; others are sensitive to the thickness and/or type of the paper toweling being dispensed; others are limited with respect to the size of paper towel roll and/or the roll core size.
Various attempts have been made to minimize a false transfer. For example, U.S. Hedge et al. Pat. No. 4,165,138 discloses a transfer assembly which does not rely on sensing a loss of tension to trigger a transfer. However, the transfer assembly includes two or more rollers with the attendant shortcomings and a number of other parts which increase the overall complexity and cost of construction.